Stabilized chlorinated hydrocarbons



United States Patent 3,397,246 STABILIZED CHLORINATED HYDROCARBONS Anclr Gustave Ryckaert, Uccle-Brussels, Belgium, and Charles Domen, deceased, late of Etterbeek-Brussels, Belgium, by Lucie Domen ne Depauw, heir, Etterbeek- Brussels, Belgium, assignors to Solvay & Cie, Brussels, Belgium, a Belgian company No Drawing. Continuation-impart of application Ser. No. 323,215, Nov. 13, 1963. This application Apr. 26, 1966, Ser. No. 545,307

' 6 Claims. (Cl. 260652.5)

ABSTRACT OF THE DISCLOSURE Chlorinated hydrocarbons are stabilized by the addition of two synergistic substances, one beingpyrrole, N-methylpyrrole, N-ethylpyrrole or (2-pyrryl)-trimethylsilane and the other being glycidol, glycidyl acetate, epoxycyclopentanol, 2 methyl 1,2-epoxypropanol-(3), S-methoxy- 1,2-epoxypropane or 3-ethoxy-1,2-epoxypropane.

This is a continuation-in-part of application Ser. No. 323,215, filed Nov. 13, 1963, now abandoned.

The present invention concerns a process for the stabilization of chlorinated hydrocarbons in order to prevent the decomposition of these products and the simultaneous formation of oxidation products during their manufacture, storage, or application.

It is known that, under the action of heat and oxygen, chlorinated hydrocarbons are subjected to an oxidation which is catalyzed by different agents such as light and certain metal salts, in particular the salts of iron, aluminium, and magnesium.

It has already been proposed to retard this oxidation by the addition of small quantities of various products to these chlorinated hydrocarbons, such as alcohols, phenols, epoxide compounds, basic mineral or organic products, etc. The use of pyrrole has been known for a long time; that of N-alkylpyrroles has been described in US. Patent No. 2,492,048. I

The conjoint application of two or more stabilizers which exert a synergistic effect has also been employed. Thus, in a previous patent by the applicants (Belgian Patent No. 563,604), is was shown that the simultaneous addition of phenol, an epoxide compound and of pyrrole or a pyrrole derivative gives results better than the sum of the stabilizing activities of the three separate compounds.

It has now been found that a high synergistic activity can be obtained by the use of mixtures consisting of pyrrole or a derivative of pyrrole, as well as an epoxide compound chosen from those which contain at least 3,397,246 Patented Aug. 13, 1968 one other oxygen function in their molecule. This other oxygen function may for instance be an alcohol, ester, or ether function. Pyrrole and derivatives thereof are sometimes conveniently referred to in the present specification and claims as pyrryl compounds.

In particular, it has now been found that chlorinated hydrocarbons are stabilized highly synergistically by a mixture of a pyrryl compound selected from the group consisting of pyrrole, N-methylpyrrole, N-ethylpyrrole, and (2-pyrryl)-trimethylsilane, and an epoxide selected from the group consisting of glycidol, glycidyl acetate, epoxycyclopentanol, 2-methyl-1,2-epoxypropanol-(3), 3- methoxy-1,2-epoxypropane, and 3-ethoxy-1,2-epoxypropane.

While the synergistic mixtures of the invention are useful for the stabilization of chlorinated hydrocarbons in general, they are particularly useful for the stabilization of trichloroethylene and perchl-oroethylene.

The stabilizing activity of various compounds and systems of compounds employed for the purpose of improving the resistance of chlorinated hydrocarbons to decomposition is demonstrated by an accelerated laboratory test carried out as follows:

150 cc. of trichloroethylene and an aluminium sample are placed in the 300 cc. flask of a Soxhlet extraction apparatus fitted with a cc. extractor. The flask is heated electrically and the trichloroethylene is rapidly brought up to the boil, so as to reflux at a constant rate while a current of oxygen is passed through the apparatus and while it is illuminated by a fluorescent lamp of the Blue Actinic type. During the entire duration of the test, the rate of liberation of acidic vapours is measured at the outlet from the apparatus. This rate, which is very slow at the start, suddenly becomes faster as the trichloroethylene blackens and is converted to a tar-like black mass. The resistance of the trichloroethylene to the test is measured in terms of the time, expressed in hours, which elapses between the start of the test, as soon as the sample has come to the boil, and the instant when the liberation of acid becomes very fast and exceeds l5 10 g.- mole/hr.

Table I indicates the resistance to decomposition, determined by the foregoing test, of unstabilized trichloroethylene and of trichloroethylene which has been stabilized with various pyrryl compounds and/or epoxides. The numerical values in Table I are hours, which are determined as explained above. The values in parentheses represent the differences between the observed resistances and the sums of the resistances conferred by each constituent of a mixture taken separately, and thus indicate the presence of synergism or the presence of the converse of synergism. The latter is indicated by a negative parenthesized value and is, of course, especially undesirable.

TABLE 1 Mixtures of the invention, 1,500 mg./liter Epoxycyclo- Z-methyl- No epoxide Glycidyl acetate Glycidol pent-anol 1,2-ep0xypropanol-(3) No pyrryl compound 22 38 42 2 33 Pyrrole, 200 mg/liter 164 260(+71) 329(+132) N-methyl-pyrrole, 200 rug/liter 176 263 (+49) 242(+24) 223(+14) N-ethyl-pyrrole, 200 mgjliter 253 579(+288) 550( 255) (2-pyrryl)-trimethylsilane, 200 rug/liter 89 134(+12) Mixtures of the invention, Mixtures comprising a simple epoxide 1,500 mgJliter 3-methoxy- 3-ethoxy- Epichlor- 1,2-epoxy- Diisobutylene 1,2-epoxy- 1,2-epoxyhydrin butane oxi e propane propane Nopyrryl compound 42 26 87 30 44 Pyrrole, 200 nig./liter 22 (+14) 260(+) 174(77) 204(+10) N-methyl-pyrrole, 200 mgJliter. N-ethyl-pyrrole, 200 mg./11ter r 210(-) 2-pyrryD-trimethylsilane, 200 mgJliter 159(+44) 53(123) v 3 I I I 4 'TableI clearly indicates the very significant synergistic other oxygen functions. The most favorable proportions effect obtained when mixtures according to the invention are between 0.1 and 0.2 g. for the pyrryls and between are employed. By contrast, the last three columns show 1.5 and 5 g. for the epoxides, per liter of the chlorinated that simple epoxide compounds, i.e., those not having anhydrocarbon to be stabilized. other oxygen function, mixed with pyrrole or. its deriva- 5 If desired, it is possible to add other compounds, whose tives give results less than the sum of the separate effects use as such is already known, to the compositions of but for one instance in which a synergistic elfect is obstabilizing substances which constitute the invention, in tained, the magnitude of which, however, is less than that particular mineral or organic substances with an alkaline of the mixtures of the invention. The use of an epoxide reaction which modify the initial pH of the chlorinated compound containing another oxygen function with a hydrocarbon. The addition of alcohols or phenols may py y compound, In accordance W131 the o tlon, thus also be effected without departing from the scope of the leads to unexpected results. invention.

The stabihzins actlvity of various Compounds a 31 The invention is not to be construed as limited to the mm of Compounds p y [for the Purpose of P particular forms described in detail herein, since there ingfhe resistance of Chlorinated hydrocarbons to (1660111' are to be regarded as illustrative rather than restirictive. P051tion is ffulthel demonstrated y a Sticolld accelerated Thus, for example, although the stabilizing compositions laboratory t s CaTried 0111; follows! according to the invention are particularly effective in I t 300 fl Of SOXhlet extraction PP the case of the stabilization of trichloroethylene and fitted with a 65 cc. extractor are placed 150 cc. of perrchloroethylene, they may equally well be employed Chlofoethylene and a X 50 X test-piece Taken for the stabilization of other chlorinated hydrocarbons,

from a cold-rolled Thomas steel having the following P such as carbon tetrachloride, dichloroethane, trichlorocent composltwn: ethane, and the like.

C 012 What is claimed and desired to secure by Letters P 0,04 Patent is:

S 005 1. A stabalized aliphatic chlorinated hydrocarbon con- Mn 047 sisting essentially of said chlorinated hydrocarbon and Si 0,01 a stabilizing amount of a synergistic mixture of a pyrryl Cu 0,04 compound selected from the group consisting of pyrrole, A1 0.01 N-methylpyrrole, N-ethylpyrrole, and (2 pyrryl) tri- N 0.017 methylsilane and an epoxide selected from the group cont' of l 'dol, l cid l acetate, e ox c clo ntanol, An even larger test-piece of the same steel is placed in the gi ig f g z g 3 g g g: 6P extractor. The flask is heated electrically and the perchlopropane .1,2- poxypropane. methylene ls rapldly f up to the boll so as to 2. A stabilized chlorinated hydrocarbon according to at a constant rate Whlle a gentle 'i fi (ixygen 1s claim 1, wherein the chlorinated hydrocarbon is trichloropassed through the apparatus and while it is illuminated by ethylene. a fluorescent lamp of the dayhght y The heatmg 1S 3. A stabilized chlorinated hydrocarbon according to cautioned so that the extractor P l Wary hour The claim 1, wherein the chlorinated hydrocarbon is perchlorotest 1s stopped after 48 hours. The acidity of the perchloroethylene ethylen-e reslfltmg after the above-descnlled procedure. is 40 4. A stabilized chlorinated hydrocarbon according to determlned 1n the aqueous extract obtained by shaking claim 1 wherein the concentration of Said py y comb one volume of perchloroethylene with an equal volume of d j b t 0 OS to 0 5 ram er liter and the concen demineralized water. The acidity is expressed in terms of g t 10 milliequivalents of hydrogen chloride per liter of perg g fg zs zi g ls i g g g gg g gf chlororethylene.

Table II indicates the resistance to decomposition, de- Wherem the concentfatlon 9 Sald PY 'Y p -l 15 about 0.05 to 0.5 gram per liter and the concentration of termined by the last described test, of unstabilized perchloroethylene and of perchloroethylene which has been stasald epoxlde 15 about 0.5 to 10 grams per liter. bilized with various pyrryl compounds and/or epoxides. 6. Stabilized perchloroethylene according to claim 3,

TABLE II l No E oxid E iehlor- Gl cidol 3Methoxy1, 2- Glycidyl Epox de (1,500 mg Inter) p e li ydrin y Epoxypropane Acetate Acidity at the end of the test, in milllequivalents of HCl/liter:

No pyrryl compound 960 640 860 1, 110 1, 340 Pyrrole (25 mg.lliter) 168 4.16 0. 90 N-methylpyrrole (25 mg. 0.08 0.04 0 0.02 0

Table II further indicates the very significant synergistic wherein the concentration of said pyrryl compound is etfect obtained when mixtures according to the invention about 0.05 to 0.5 gram per liter and the concentration of are employed. The second column shows that a mixture said epoxide is about 0.5 to 10 grams per l1ter. of a simple epoxide compound, i.e., one not having an- References Cited other ox en function, and a p rrole or its derivatives decreases cl e composition of the gerchloroethylene to a sig- UNITED STATES PATENTS nificantly lesser extent than mixtures according to the 2,797,250 6/ 1957 Copefin 260-6525 invention of epoxide compounds having another oxygen 2,371,645 3/1945 Aitchison et al. 260-6525 function and a pyrryl compound. 2,973,392 2/ 1961 Graham 260652.5 The quantities of stabilizing substances to be employed 3,188,355 6/1965 Petering 260--652,5

according to the invention are generally within the range of 0.05 and 0.5 g./l. for the pyrryl compounds and 0.5 LEON ZITVER Pnmary Ex ammer' to 10 g./l. for the epoxide compounds having one or more M. JACOB, Assistant Examiner. 

